Additive composition, method of blending same and a low haze polyolefin material and preparation thereof

ABSTRACT

The present invention relates to an additive composition and a low haze polyolefin material which may be prepared using said additive composition. In particular, the polyolefin material is prepared from a polyolefin resin composition comprising one or more optical brighteners, bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitol at a certain weight ratio. In an aspect, the present invention relates to a method for forming a polyolefin material; said method comprising:
         (i) preparing a polyolefin resin composition comprising polyolefin resin, one or more optical brighteners, bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitol, wherein the weight ratio of bis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitol in the polyolefin resin composition is 45:55 to 25:75;   (ii) processing said polyolefin resin composition to form said polyolefin material.

The present invention relates to an additive composition and a low hazepolyolefin material which may be prepared using said additivecomposition. In particular, the polyolefin material is prepared from apolyolefin resin composition comprising one or more optical brighteners,bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidenesorbitol, wherein bis-3,4-dimethylbenzylidene sorbitol andbis-p-ethylbenzylidene sorbitol are present in a ratio such that a lowhaze polyolefin material can be prepared at lower than conventionalprocessing temperatures.

Dibenzylidene sorbitol (DBS) derivatives are a well-known class ofnucleating agents/clarifying agents for modifying the crystallizationprocess of polyolef in resins. Such compounds are known to: shortencycle times (i.e. the time required to mould a single plastic part), asa result of more rapid solidification; improve mechanical properties,such as stiffness and heat resistance; and improve the opticalproperties of plastics, such as haze level, by eliminating largespherulites which scatter light (and are therefore also referred to asclarifying agents). These effects have, inter alia, allowedpolypropylene and linear low density polyethylene plastics prepared withDBS derivatives to be used in place of expensive polyethyleneterephthalate or polystyrene for containers and packaging products whichrequire good optical clarity.

Unlike alternative nucleating agents, such as metal salts, silica andthe like, DBS derivatives must typically be melted and uniformlydispersed/dissolved in the molten resin. Subsequent recrystallization ofthe DBS derivative forms a fine crystalline network providing nucleationsites, which reduce the size of spherulites formed in the resin as itcools, thereby reducing light scattering and improving clarity. Inconventional moulding methods comprising the step of injecting orextruding a polyolefin resin containing a DBS derivative, thetemperature of the molten resin is appreciably higher than the sol-geltransition temperature of the melt during the heating cycle.Furthermore, use of a nucleating agent having a high melting point hasthe disadvantage that the resin composition containing it must bemoulded at commensurately high temperatures in order to solubilize thenucleating agent, leading to significant energy consumption.

For example, a crystalline resin composition containing as a nucleatingagent either 1,3:2,4-bis(polyalkylbenzene)sorbitol or an unsymmetricalDBS derivative (wherein the two aromatic rings have differentsubstituents) may provide a moulded article exhibiting desirable opticalproperties. However, the melting point of such nucleating agents is ashigh as 260° C., and so the resin composition must typically beprocessed at a correspondingly high temperature, so as to obtainadequate dissolution of the nucleating agent in the resin composition.If processing temperatures are too low, insufficient dissolution of thenucleating agent will result; leading to unsatisfactory levels of hazein the resulting polyolef in material.

As processing temperature is increased to accommodate such high meltingpoint nucleating agents, energy consumption is also increased,undesirably. Furthermore, the cycle time for processing the plasticarticle may also be lengthened as a result of longer cooling periods.This negates advances continuously being made in lowering thetemperature profiles of polyolefin resins, particularly polypropylene,such that melting temperatures are lowered and brought closer tocrystallisation temperatures, which can reduce cooling periods andtherefore cycle times. In a climate of ever-increasing energy prices,high processing temperatures can in effect preclude the economicviability of plastics preparation. Additionally, another problem thatmay arise with high processing temperatures is that DBS derivatives cansublimate when heated to temperatures near their melting points, forinstance during the high temperature moulding operation, leading tounwanted re-deposition on moulding equipment (i.e. “plate-out”).

U.S. Pat. No. 5,198,484 describes a process of milling sorbitol andxylitol nucleating agents to ultrafine particle size and “dissolving” inthe resin at a temperature below that of the melting point of theparticular nucleating agent. It was, however, noted in U.S. Pat. No.5,198,484 (Example 3) that the clarifying agent is not necessarilyhomogenously distributed throughout the resin. This can lead tonon-uniform haze reduction across the resulting plastic. Indeed, thereis the possibility of opaque patching across the resulting plasticarticle, which is unlikely to be aesthetically acceptable as a consumerproduct. Another problem that arises as a result of the inhomogeneity ofdistribution of the nucleating agent is irregular spheruliticorganization, meaning that the polymer micro-structure is not uniformlymodified by the addition of the nucleating agent, as intended. This cannegatively impact upon the macroscopic properties of the resultingplastic article and potentially make it unfit for purpose. Moreover, theprocess involves milling which requires additional equipment andprocessing steps, which outweigh any cost savings associated withprocessing at lower temperatures, at least in the short term.

A particularly preferred, but high cost, DBS derivative having a highnucleating efficiency and affording good organoleptic properties isbis-3,4-dimethylbenzylidene sorbitol (3,4-DMDBS). However, the use of3,4-DMDBS requires high processing temperatures, otherwise there is aproblem of unacceptable levels of haze in polyolefin articles preparedwith this agent when processing temperatures are lower than 230° C. U.S.Pat. No. 7,351,758 and its corresponding continuation, U.S. Pat. No.7,501,462, describe using a blend of 3,4-DMDBS and DBS (unsubstituted)nucleating agents to try and address this issue. However, improvementsat lower processing temperatures, for example below 210° C., were onlyobserved with polypropylene resins exhibiting high melt flow values ofat least 20, preferably at least 50; which may require the use of a“vis-breaking agent” in order to reduce the viscosity of the polyolefinresin and increase the melt flow index.

U.S. Pat. No. 6,989,154 discloses a blend of 3,4-DMDBS andp-methyldibenzylidene sorbitol (MDBS) as a lower cost alternative tousing 3,4-DMDBS alone as a clarifying agent. It is reported that theblend confers a good degree of clarification in terms of the haze levelin polyolef in articles prepared using the blend. However, U.S. Pat. No.6,989,154 teaches that the blend of 3,4-DMDBS and MDBS must be used in aresin composition processed at conventional high processingtemperatures. Indeed, according to the example described in theexperimental section of U.S. Pat. No. 6,989,154, the melt temperature ofthe resin and additive composition upon exit of the extruder die was ashigh as 246° C., whilst the moulder barrel was reportedly set to 220° C.Clearly, energy consumption in preparing a clarified polyolefin materialas described in U.S. Pat. No. 6,989,154 is still very high.

U.S. Pat. No. 6,989,154 also describes alternative blends, including:3,4-DMDBS/DBS; 3,4-DMDBS/EDBS; or 3,4-DMDBS/TDBS(1,3;2,4-bis(5′,6′,7′,8′-tetrahydro-2-naphthylidene) sorbitol). However,these blends are reported not to exhibit any of the benefits of the3,4-DMDBS/MDBS blend, as illustrated in results of the comparativeexamples in Table 2 of that document, which were processed undersimilarly high processing temperatures.

There remains a need for a means for broadening the range of temperatureover which nucleated and clarified polyolefin materials may suitably beprepared by lowering the effective minimum processing temperature,without compromising haze values or organoleptic properties and whilstavoiding the problems or limitations associated with the prior artmentioned hereinbefore.

The present invention is based on the unexpected discovery thatbis-3,4-dimethylbenzylidene sorbitol (3,4-DMDBS) andbis-p-ethylbenzylidene sorbitol (EDBS) (depicted below) exhibit asurprising synergy, when used in combination.

Specifically, when these agents are added to a polyolefin resin in a3,4-DMDBS to EDBS weight ratio of from 45:55 to 25:75, the minimumtemperature at which the blend is soluble in the molten polyolef inresin (“solubility point”) is consistently lower than for either of theindividual agents of the blend alone. Furthermore, not only is theresynergy between the components of the blend in terms of solubility inmolten polyolefin resin, the blend also exhibits synergy with respect totransparency in the resulting nucleated and clarified polyolefinmaterial prepared therefrom. Furthermore, this synergy is not impactedby the presence of one or more optical brighteners, which can furtherenhance desirable optical properties in the resulting nucleated andclarified polyolefin material, which is surprisingly obtainable at lowprocessing temperature.

When 3,4-DMDBS and EDBS are added to a polyolefin resin in the aboveweight ratio and a polyolefin material is prepared therefrom at lowerthan conventional processing temperatures (e.g. below 200° C.), hazevalues exhibited by the polyolef in material are lower than for eitherof the agents of the blend alone. Synergistic effects are alsoconsidered to be illustrated by the finding of the inventors that blendsof 3,4-DMDBS and EDBS, in the weight ratios according to the presentinvention, form a eutectic system, meaning that the melting point of theparticular blend is lower than that of either of 3,4-DMDBS or EDBSalone.

Accordingly, the blend of 3,4-DMDBS and EDBS provides a means foreffectively nucleating and clarifying a polyolefin resin at lower thanconventional processing temperatures, thereby reducing energyconsumption, whilst affording a polyolefin material having desirableoptical properties. Furthermore, the present invention may be used forbroadening the effective processing temperature range over which adesirably low haze polyolefin material may be prepared.

Thus, in a first aspect, the present invention provides a method forforming a polyolef in material, said method comprising: (i) preparing apolyolefin resin composition comprising polyolefin resin, one or moreoptical brighteners and bis-3,4-dimethylbenzylidene sorbitol andbis-p-ethylbenzylidene sorbitol, wherein the weight ratio ofbis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitolin the polyolef in resin composition is from 45:55 to 25:75; and (ii)processing said polyolefin resin composition to form said polyolefinmaterial.

Preferably, processing of the polyolefin resin composition to form saidpolyolefin material is conducted at a temperature of from 180° C. to245° C., preferably from 185° C. to 230° C. Other preferred processingtemperature ranges used in the preparation of the polyolefin materialinclude: 200° C. or below, for example from 180° C. to 200° C., morepreferably from 185° C. to 198° C., even more preferably at atemperature of from 190° C. to 197° C., most preferably from 190° C. to195° C.

In another aspect, the present invention also provides a method forreducing haze in a polyolefin material which is prepared by processing apolyolefin resin composition; said method comprising combining apolyolefin resin, one or more optical brighteners,bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitolto form a polyolefin resin composition such that the weight ratio ofbis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitolin the polyolefin resin composition is 45:55 to 25:75, prior toprocessing of the polyolef in resin composition into the polyolefinmaterial.

Preferably, processing of the polyolefin resin composition to form saidpolyolefin material is conducted at a temperature of from 180° C. to245° C., preferably from 185° C. to 230° C. Other preferred processingtemperature ranges used in the preparation of the polyolefin materialinclude: 200° C. or below, for example from 180° C. to 200° C., morepreferably from 185° C. to 198° C., even more preferably at atemperature of from 190° C. to 197° C., most preferably from 190° C. to195° C.

In an alternative aspect, the present invention also provides a methodfor forming a polyolef in material; said method comprising: (i)preparing a polyolefin resin composition comprising polyolefin resin,one or more optical brighteners, bis-3,4-dimethylbenzylidene sorbitoland bis-p-ethylbenzylidene sorbitol, wherein the weight ratio ofbis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitolin the polyolefin resin composition is 45:55 to 15:85; (ii) processingsaid polyolefin resin composition to form said polyolefin material; andwherein processing of the polyolef in resin composition to form saidpolyolefin material is conducted at a temperature of no more than 200°C.

In this alternative aspect of the invention, a broader weight ratio ofbis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitol(compared with the first aspect) may be utilised and also haveadvantages over the use of either of bis-3,4-dimethylbenzylidenesorbitol or bis-p-ethylbenzylidene sorbitol alone, when processing ofthe polyolef in resin composition to form said polyolefin material isconducted at a temperature of no more than 200° C.

Preferably, processing of the polyolefin resin composition to form saidpolyolefin material is conducted at a temperature of from 180° C. to200° C., more preferably from 185° C. to 198° C., even more preferablyat a temperature of from 190° C. to 197° C., most preferably from 190°C. to 195° C.

Reference herein to a “polyolefin resin composition” is intended torefer to a polyolef in resin in which the combination of one or moreoptical brighteners, 3,4-DMDBS and EDBS has been dissolved. Thus, thepreparation of the polyolefin resin composition in accordance with thepresent invention may, for instance, comprise dissolving, one or moreoptical brighteners, 3,4-DMDBS and EDBS in a molten polyolefin resin atthe specific weight ratio of 3,4-DMDBS to EDBS as described herein. Aswill be appreciated, additional clarifying and nucleating agents may bepresent in the polyolefin resin composition, provided that the weightratio of 3,4-DMDBS to EDBS in the composition remains as defined herein.

Reference herein to a “polyolefin material” is intended to refer to anythermoplastic article or object which may suitably be prepared fromprocessing a molten polyolefin resin composition as described herein,for instance by extrusion or injection moulding at a processingtemperature described hereinabove.

The combination of bis-3,4-dimethylbenzylidene sorbitol andbis-p-ethylbenzylidene sorbitol used in accordance with the presentinvention has surprisingly been found to exhibit synergistic effects interms of the solubility in a molten polyolefin resin and in terms of thetransparency afforded to a nucleated and clarified polyolefin materialobtained therefrom. As a result, the processing temperature over which anucleated and clarified polyolefin material exhibiting low haze may beeffectively prepared is broadened considerably and covers temperaturesmuch lower than those which are feasible with conventional sorbitolbased clarifying agents used alone, or combined in known blends.Furthermore, these advantageous effects are not diminished by thepresence of one or more optical brighteners which can further enhancethe desirable optical properties obtained in the nucleated and clarifiedpolyolefin material, which properties are surprisingly obtainable at lowprocessing temperature.

In particular, blends of bis-3,4-dimethylbenzylidene sorbitol andbis-p-ethylbenzylidene sorbitol in accordance with the present inventionconsistently exhibit solubility points in molten polyolefin resins whichare lower than those of the two sorbitol components individually at thesame concentration as that of the total blend concentration.Alternatively or additionally, blends of bis-3,4-dimethylbenzylidenesorbitol and bis-p-ethylbenzylidene sorbitol in accordance with thepresent invention may confer haze values in a nucleated and clarifiedpolyolefin material prepared therefrom which are lower than those of thetwo sorbitol components individually at the same concentration as thatof the total blend concentration.

Reference herein to “solubility point” is intended to refer to theminimum temperature at which the clarifying/nucleating agents and blendsthereof become completely dissolved in a molten polyolefin resincomposition, in the absence of any applied shear to the composition. Thesolubility point (° C.) is defined as the maximum peak in a plot ofrelative brightness variability versus temperature. Changes in lighttransmittance in a compounded admixture of resin andclarifying/nucleating agents may be observed as temperature is graduallyincreased using a microscope (e.g. a BX41, Olympus) with hot stage (e.g.FP90, Mettler) coupled to an image capturing device, such as amicroscope digital camera system (e.g. Olympus DP11 or PixeLINKMicroscopy Camera), so as to continuously capture images (i.e.photomicrographs/video) of the compounded admixture during heating.Brightness of individual images and brightness variability betweensuccessive images may then be determined by means of an analysis unitcoupled to the image capturing device. The analysis unit may take theform of a computer system comprising a software package configured forprocessing the brightness/light transmittance data relating to thecaptured images (for example, PixeLINK Microscopy Software). From thebrightness data, the solubility point may be determined based on thetemperature at which maximum relative brightness variability is observedin a plot of relative brightness variability versus temperature.

The change in the physico-chemical properties of the molten composition,for instance in terms of the loss of crystallinity of the blend ofnucleators in the molten resin, gives rise to changes in the lighttransmittance through the molten composition and hence the brightness ofthe captured images obtained by the camera system. Brightnessvariability (i.e. change in brightness between successive capturedimages during heating) reaches a peak upon complete dissolution of theblend of nucleators and corresponds to a maximum in relative brightnessvariability. Further increases in temperature after complete dissolutionhave little effect on brightness therefore brightness variability aftercomplete dissolution of the blend of nucleators is minimal betweensuccessive captured images. This explains why the dissolution may bevisualized as a peak in a plot of relative brightness variabilityagainst temperature; the temperature at which the peak in relativebrightness variability is observed corresponding to the solubilitypoint.

As will be appreciated, although the solubility point represents theminimum temperature at which all of the clarifying/nucleating agents andblends thereof become completely dissolved in the resin composition, asignificant degree of dissolution may be observed at temperatures belowthe solubility point, particularly in the presence of shear.

Reference herein to “haze value” is intended to refer to the amount oftransmitted light that is scattered upon passing through a film or sheetof material. Haze values reported herein were determined following ASTMmethod D1003-61 (“Standard Test Method for Haze and LuminousTransmittance of Transparent Plastics”) and are quoted together with thespecific plaque thickness (e.g. 0.5 mm or 1 mm) of the test material,the temperature under which the polyolefin resin is injection moulded(e.g. 180° C., 190° C. or 200° C.), and the total content of clarifyingagent in the resin. Haze may be measured using, for instance, a hazemeter such as BYK Gardner Haze Guard Plus.

Reference herein to the “temperature at which processing of the resincomposition is conducted” or the “processing temperature” is intended torefer to the temperature at which the molten polyolefin composition isprocessed in order to prepare the polyolefin material. Thus, theprocessing temperature includes the mould temperature (e.g. injection orextrusion moulding) of the molten polyolefin composition. As will beappreciated, higher temperatures may be employed to ensure dispersionand dissolution of the combination of 3,4-DMDBS and EDBS in thepolyolefin resin than are subsequently employed for processing (i.e.moulding) the resulting polyolef in composition, provided that theprocessing temperature does not preclude the advantageous effects of thecombination of 3,4-DMDBS and EDBS. For instance, complete dissolution of3,4-DMDBS and EDBS in the molten polyolefin resin may be achieved at orabove the solubility point of the particular combination of 3,4-DMDBSand EDBS in the resin. However, in at least some embodiments, theprocessing temperatures used for moulding the polyolefin composition maybe lower than the solubility point of the combination of 3,4-DMDBS andEDBS in the resin, without there being plate-out or precipitation of3,4-DMDBS and EDBS so as to preclude a positive effect on hazeproperties. It will also be appreciated that satisfactory dispersion anddissolution of the combination of 3,4-DMDBS and EDBS may also beachieved in the resin at temperatures lower than the solubility point ofthe blend in a particular resin, which as described above is measured inthe absence of shear. This is illustrated, for instance, in FIG. 1(described hereinbelow) which shows that significant dissolution of aclarifying/nucleating agent in a resin composition may be achieved attemperatures which are lower than the measured solubility point.

In accordance with the present invention, a polyolefin resin compositionmay be prepared by dissolving one or more optical brighteners, 3,4-DMDBSand EDBS at the specific 3,4-DMDBS to EDBS weight ratio describedhereinbefore in a molten polyolef in resin. The resulting polyolefinresin composition is thus particularly useful as feedstock for theproduction of a polyolefin material having desirably low haze, even whensaid material is produced under lower than conventional processingtemperatures (e.g. less than 200° C.).

Thus, in a further aspect, the present invention also provides anucleating and clarifying additive composition comprising or consistingessentially of one or more optical brighteners, 3,4-DMDBS and EDBS,wherein the weight ratio of 3,4-DMDBS to EDBS in the additivecomposition is 45:55 to 25:75. Preferably the weight ratio of 3,4-DMDBSto EDBS in the additive composition is 40:60 to 25:75; more preferablywherein the weight ratio of 3,4-DMDBS to EDBS 35:65 to 25:75; mostpreferably wherein the weight ratio of 3,4-DMDBS to EDBS is 32:68 to28:72, for example 30:70.

The nucleating and clarifying additive composition of the presentinvention may further comprise common commercial additives in additionto the one or more optical brighteners, 3,4-DMDBS and EDBS, provided theratio 3,4-DMDBS to EDBS remains as defined above and provided anyadditional nucleating and/or clarifying agents do not interfere with theadvantageous effects of the combination of 3,4-DMDBS and EDBS.

In yet a further aspect, the present invention also provides apolyolefin resin composition; comprising: (a) polyolefin resin; (b)bis-3,4-dimethylbenzylidene sorbitol; (c) bis-p-ethylbenzylidenesorbitol; and (d) one or more optical brighteners; wherein the weightratio of bis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidenesorbitol in the polyolef in resin composition is from 45:55 to 25:75.Preferably wherein the weight ratio of 3,4-DMDBS to EDBS in thepolyolefin resin composition is 40:60 to 25:75; more preferably whereinthe weight ratio of 3,4-DMDBS to EDBS 35:65 to 25:75; most preferablywherein the weight ratio of 3,4-DMDBS to EDBS is 32:68 to 28:72, forexample 30:70.

In a still further aspect, the present invention provides a polyolefinmaterial comprising: (a) polyolefin; (b) bis-3,4-dimethylbenzylidenesorbitol; (c) bis-p-ethylbenzylidene sorbitol; and (d) one or moreoptical brighteners; wherein the weight ratio ofbis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitolin the polyolefin material is from 45:55 to 25:75.

Preferably wherein the weight ratio of 3,4-DMDBS to EDBS in thepolyolefin material is 40:60 to 25:75; more preferably wherein theweight ratio of 3,4-DMDBS to EDBS 35:65 to 25:75; most preferablywherein the weight ratio of 3,4-DMDBS to EDBS is 32:68 to 28:72, forexample 30:70. Preferably, the polyolef in (a) is selected from thegroup consisting of polypropylene, polyethylene, polybutylene, or blendsor copolymers thereof. Most preferably, polyolefin (a) is polypropyleneor a copolymer thereof.

In another aspect, the present also provides a polyolefin materialprepared by a method as described herein.

The polyolef in resin used in accordance with the present inventionrefers to any a stereoregular, crystalline resin which may suitably beused for preparing a polyolef in material having low haze. Examples ofsuitable polyolefin resins include polyethylene resins, polypropyleneresins, polybutylene resins, or blends or copolymers thereof.Preferably, the polyolefin resin is selected from polypropylene resins.

There is no specific restriction on the production method, type ofstereoregularity, crystallinity, type, components of a blend, or themolecular weight distribution of the polyolefin resins. Examples of thepolyethylene resins include high-density polyethylene, medium-densitypolyethylene, low-density polyethylene, linear low-density polyethyleneand ethylene copolymers with an ethylene content of 50 wt. % or more.Examples of polypropylene resins include isotactic or syndiotacticpropylene homopolymers and propylene copolymers with a propylene contentof 50 wt. % or more. Examples of polybutene resins include isotactic orsyndiotactic butene homopolymers and butene copolymers with a butenecontent of 50 wt. % or more.

The above copolymers may be random copolymers (“RACO”), homo- orblock-copolymers. For example, the polyolefin resin may be apolypropylene random compolymer (RACO). Comonomers which can form theabove copolymers are, for example, C₂-C₁₆ alpha-olefins such asethylene, propylene, butene, pentene, hexene, heptene, octene, nonene,decene, undecene and dodecene; acrylic or methacrylic acid esters,particularly C₁-C₁₈ alkyl esters, such as methyl acrylate, methylmethacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butylmethacrylate, octyl acrylate, octyl methacrylate, stearyl acrylate,stearyl methacrylate and the like; vinyl acetate;1,4-endomethylenecyclohexene and like bicyclo monomers.

Catalysts useful for the production of the polymers include not onlyradical polymerization catalysts and Ziegler-Natta catalysts which arecommonly employed in the art, but also catalyst systems comprising acatalyst prepared by depositing a transition metal compound (e.g.,titanium halide such as titanium trichloride or titanium tetrachloride)on a support mainly composed of magnesium chloride or like magnesiumhalide, in combination with an alkyl aluminum compound (such as triethylaluminum or diethyl aluminum chloride) and; said catalyst systemsfurther comprising a specific ester compound and an organic ethercompound; metallocene catalysts comprising a cyclopentadiene or itsderivative and a metal of the fourth group such as titanium orzirconium; and said “metallocene catalysts” further comprisingmethylalumoxane.

The melt flow rate (MFR) of the polyolefin-based resin for use in theinvention, measured according to ASTM method D1238-04, may be suitablyselected according to the moulding method to be employed and physicalproperties required of the moulded article. Typically, the MFR for apolyolefin resin suitably varies from 0.01 to 200 g/10 min, preferablyfrom 0.05 to 100 g/10 min. In other preferred embodiments, the MFR valueof the polyolefin resin used in accordance with the present invention is5 g/10 min or above. Polyolefin resins having higher MFRs are morecompatible with lower processing temperatures. Thus, in other preferredembodiments, the MFR of the polyolefin resin may be 20 g/10 min orabove. In other preferred embodiments, the MFR of the polyolefin resinmay be 40 g/10 min or above, for example 50 g/10 min. In other preferredembodiments, the MFR of the polyolef in resin may be 70 g/10 min orabove, for example 80 g/10 min. The molecular weight distribution(Mw/Mn) of the resin is not limited, but is usually from 1 to 10.

It is known that polyolefin resins having higher MFR values, i.e. lowerviscosities, can typically be processed at lower temperature. Thus,using the combination of 3,4-DMDBS and EDBS in accordance with thepresent invention, together with polyolefin resins having higher MFRvalues, for instance 20 g/10 min or above, may be particularlyadvantageous for preparing a polyolefin material having desirably lowhaze at lower than conventional processing temperature (e.g. below 200°C.).

The polyolefin resin may be a multimodal, or bimodal or unimodalcomposition, where modality of the polymer refers to the form of itsmolecular weight distribution curve (i.e. molecular weight fraction as afunction of its molecular weight). For instance, polymer components maybe produced in a sequential step process, using reactors arranged inseries operating under different reaction conditions. Consequently, eachfraction prepared in a specific reactor will have its own molecularweight distribution. When such fractions are combined, it is possiblethat the molecular weight distribution curve of the final polymerdisplays multiple maxima, or may be substantially broadened incomparison to the molecular weight distribution curves for theindividual fractions.

One or more optical brighteners, also known as fluorescent whiteningagents (FWA), are utilized in accordance with the present invention.Optical brighteners are known to absorb ultraviolet light energy andre-emit light by fluorescence mostly in the blue region of the visiblespectrum, at a wavelength of approximately 400 to 500 nm. Opticalbrighteners can be used to reduce the appearance of yellow in materialsresulting from a “blue deficit” in the light reflected therefrom.

Any suitable optical brightener may be used in connection with thepresent invention, such as those which are known for use in improvingoptical properties of polyolefin materials and having sufficient thermalstability for extrusion or injection moulding processes associated withthe preparation of polyolefin materials. Examples of suitable classes ofthe one or more optical brighteners for use in the present inventioninclude bis-benzoxazoles, phenylcoumarins, methylcoumarins,bis-(styryl)biphenyls, and combinations thereof, which are, for example,described in detail in Plastics Additives Handbook, Hanser GardnerPublications, 6th Edition, H. Zweifel, D. Maier, M. Schiller Editors,2009.

Particularly preferred examples of optical brighteners are selected fromthe bis-benzoxazole class, namely2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene and4,4′-bis-benzoxazolyl-stilbene, which are discussed in detail in:Plastics, Additives and Compounding, Volume 5, Issue 6, June 2003.4,4′-bis-benzoxazolyl-stilbene, (CAS#: 1533-45-5), complies withregulations for indirect food additives administered by the U.S. Foodand Drug Administration at 21 CFR 178.3297 (Colorants for Polymers).4,4′-bis-benzoxazolyl-stilbene is also listed in European UnionDirective 2002/72/EC as PM/Ref. No. 38515 for use in plastics forindirect food contact. 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene(CAS #: 7128-64-5): is listed in European Union Directive 2002/72/EC asPM/Ref No. 38560 for use in plastics for indirect food contact.

Specific examples of commercially available bis-benzoxazole opticalbrighteners include: Tinopal® family from BASF, which such as TinopalABP-A, Tinopal ABP-X, Tinopal ASP, Tinopal BPO, TinopalEC, Tinopal HST,Tinopal HW, Tinopal MSP, Tinopal NP, Tinopal SPP-N, Tinopal SPP-Z,Tinopal UP HC DD, Tinopal UP, Tinopal CBS-X and Tinopal® OB; UVITEX®compounds from Ciba Specialty Chemicals, such as UVITEX® OB, UVITEX®OB-C, UVITEX® OB-P, UVITEX® FP, UVITEX® FP-C; Eastobrite® compounds fromEastman Chemical, such as Eastobrite® OB, Eastobrite® OB-1 andEastobrite® OB-3, Hostalux® compounds from Clariant, such as HostaluxACK, Hostalux CP01, Hostalux EBU, Hostalux EF, Hostalux ERE, HostaluxEREN, Hostalux ES2R, Hostalux ESR, Hostalux ETB 300, Hostalux ETBN,Hostalux KCB, Hostalux KS, Hostalux KS1 B, Hostalux KSB3, Hostalux KSC,Hostalux KSN, Hostalux NR, Hostalux NSM, Hostalux PFC, Hostalux PFCB,Hostalux PN, Hostalux PNB, and Hostalux PR, Whitefluor® compounds(bis-(styryl)-benzoxazoles) from Sumitomo Chemical Co., such asWhitefluor® B, Whitefluor® PEN, Whitefluor® PHR, Whitefluor® HCS,Whitefluor® PCS.

Specific examples of phenylcoumarins and methylcoumarins include3-phenyl-7-(4-methyl-6-butyloxybenzoxazole)coumarin and4-methyl-7-diethylamincoumarin, respectively.

Specific examples of commercially available methyl-coumarin opticalbrighteners are Eccowhite® compounds from Eastern Color & Chemical Co.,such as Eccowhite 1 132 MOD, Eccowhite 2013, Eccowhite 2790, Eccowhite5261, Eccowhite AEA-HF, Eccowhite Nylon FW, Eccowhite OP, Eccowhite PSO,Eccowhite DM-04 MOD.

The nucleating and clarifying additive composition of the presentinvention typically comprises an amount of one or more opticalbrighteners at a level which leads to an improvement in opticalproperties (for instance, a yellowness reduction) in the polyolef inmaterial prepared therefrom. Preferably, a minimum amount of the one ormore optical brighteners is used which is sufficient for achieving thedesired benefit to optical properties of the polyolefin material madetherefrom.

The amount of optical brightener in the nucleating and clarifyingadditive composition is preferably in an amount necessary to give aconcentration of the optical brightener in the nucleated and clarifiedpolyolef in material prepared therefrom of from 1 to 100 ppm, morepreferably from 2 to 50 ppm, and even more preferably from 5 to 20 ppm.In other preferred embodiments, the total amount of the one or moreoptical brighteners present in the nucleating and clarifying additivecomposition is from 0.05 to 5.0 wt. %, based on the combined weight ofbis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene present,more preferably from 0.1 to 3.0 wt %, even more preferably from 0.50 to2.0 wt %. The total amount of the one or more optical brighteners in thepolyolefin resin composition according to the present invention ispreferably from 1 to 100 ppm, by weight of the polyolefin resincomposition, more preferably from 2 to 50 ppm, and even more preferablyfrom 5 to 20 ppm, by weight of the polyolefin resin composition.

The polyolefin resin for use in the present invention may contain, wherenecessary, rubbers, for the purpose of improving the low-temperatureproperties and impact resistance of the resin. For instance, thepolyolefin resin may contain ethylene-propylene rubbers, SBR,hydrogenated SBR, SBS block copolymers, hydrogenated SBS blockcopolymers, hydrogenated styrene-isoprene (S-I) block copolymers orhydrogenated S-I-S block copolymers.

Furthermore, where necessary, rigidity-imparting nucleating agents orfillers can also be added to the polyolef in resin in an amount whichdoes not compromise the effects of the present invention (e.g., up toabout 50 wt. parts, in particular about 0.01 to 20 wt. parts, per 100wt. parts of the polyolefin resin). For instance, talc, hydrotalcite,mica, zeolite, perlite, diatomaceous earth, calcium carbonate andaluminum hydroxy-bis-tert-butylbenzoate may be added to the polyolefinresin.

Where necessary, the polyolefin resin for use in the invention maycontain pigments. Various pigments including white pigments are usable,but colour pigments are preferred. Examples of useful pigments includetitanium oxide pigments (for instance, titanium dioxide, titanium yellowand titanium black), zinc oxide, chromium oxide, zinc sulfide, carbonblack, iron oxide pigments (for instance, iron oxide, yellow oxide, redoxide), cadmium sulfide pigments (for instance, cadmium yellow, andcadmium mercury red), barium sulfate, ultramarine, cobalt blue,phthalocyanine pigments (for instance, phthalocyanine green, andphthalocyanine blue), isoindolinone pigments (for instance,isoindolinone yellow, and isoindolinone red), azo pigments (forinstance, permanent red FSR, and pigment scarlet 3B), quinacridonpigments, anthrapyrimidine pigments (for instance, anthrapyrimidineyellow), benzidine pigments (for instance, benzidine orange GR),indanthrene pigments (for instance, indanthrene brilliant orange) andmanganese violet. Pigment may be used in an amount that does notcompromise the effects of the invention. Typically, it is used in anamount of from 1 to 500 ppm of the polyolefin resin composition.

The polyolefin resin for use in the present invention may contain otheradditives such as stabilizers, neutralizing agents, antistatic agents,and lubricants. These known additives may be used in combination,insofar as they do not compromise the effects of the invention.

3,4-DMDBS and EDBS, used in accordance with the present invention, arereadily available from commercial sources as powders, or they can bemade by methods familiar to the skilled person. For instance, 3,4-DMDBSand EDBS may be prepared by the methods described in U.S. Pat. Nos.4,429,140 or 4,902,807 (assigned to New Japan Chemical Co., Ltd), whichmethods involve the reaction of sorbitol with a substituted benzaldehydeor alkyl acetal derivative thereof. Suitable commercial 3,4-DMDBSproducts include Geniset® DXR from New Japan Chemical Co., Ltd andMillad® 3988 from Miliken Chemical.

Any suitable means for admixing the one or more optical brighteners,3,4-DMDBS, EDBS and polyolefin resin of which the skilled person isaware may be used for forming the polylef in composition. The method foraddition of the one or more optical brighteners, 3,4-DMDBS and EDBS tothe polyolefin resin in order to form the polyolefin resin compositionaccording to the invention is thus not specifically limited, although itis preferable to use a single-stage addition method wherein the one ormore optical brighteners and nucleating and clarifying agents are addedto the resin directly, at the required ratio. However, a two-stageaddition method can also be employed, wherein the nucleating andclarifying agents are added in the form of a masterbatch having aconcentration of about 2 to about 15% by weight, provided the batchcontains the agents in the required ratio. Dissolution of the one ormore optical brighteners, 3,4-DMDBS and EDBS in a polyolefin resincomposition may be enhanced by increasing the levels of shear duringresin processing. For instance, use of a twin screw extruder in favourof a single screw extruder when compounding is known generally toencourage dissolution.

In a number of aspects of the invention described herein, the weightratio of 3,4-DMDBS to EDBS which is used is 45:55 to 25:75. Preferably,the weight ratio of 3,4-DMDBS to EDBS is 40:60 to 25:75, more preferably35:65 to 25:75, most preferably 32:68 to 28:72, for example 30:70. Thesynergistic effects of the blends are achievable with these weightratios of 3,4-DMDBS to EDBS. Synergistic effects are also noticeableacross a broader range of weight ratios, in particular where the weightratio of 3,4-DMDBS to EDBS which is used is from 45:55 to 15:85, whenprocessing of the polyolefin resin composition to form said polyolefinmaterial is conducted at a temperature of no more than 200° C.

In particular, these blends exhibit a surprising synergy giving rise toparticularly low solubility points, which mean that lower temperaturescan be used to dissolve the nucleating and clarifying agents in themolten polyolefin resin in order to form the polyolef in resincomposition. Moreover, lower processing temperatures can be used whenthe polyolef in resin composition is processed (e.g. moulded) to formthe nucleated and clarified polyolefin material in accordance with theinvention. Polyolefin materials prepared at lower than conventionalprocessing temperatures, for instance lower than 200° C., have also beenfound to exhibit haze values which are lower than if either of 3,4-DMDBSand EDBS of the blends was used alone. These effects are clearly ofparticular advantage for broadening the range of temperature over whicha low haze polyolefin material may suitably be prepared, as well as forpreparing desirable polyolefin materials with reduced energyconsumption. Furthermore, the high level of shear developed whenadmixing 3,4-DMDBS, EDBS and the polyolefin resin and subsequentlyprocessing the composition enhances dissolution of 3,4-DMDBS and EDBS.Consequently, adequate levels of dissolution may thus be achieved in theresin composition at processing temperatures which are even lower thanthe solubility points of the blend of 3,4-DMDBS and EDBS used inaccordance with the invention. Furthermore, these advantageous effectsare not diminished by the presence of the one or more opticalbrighteners which can further enhance the desirable optical propertiesobtained in the nucleated and clarified polyolefin material, whichproperties are surprisingly obtainable at low processing temperature.

If lower moulding temperatures are used, then the time lag before thepolyolefin material is removed from the mould (i.e. the cooling periodfor reaching the relevant crystallisation point of the polyolef in resincomposition) may be reduced. This can shorten cycle times and increaseprocess efficiency.

At low processing temperatures (e.g. below 200° C.), EDBS alone as aclarifying and nucleating agent may exhibit good solubility in themolten polyolefin resin, whilst also conferring a satisfactory level oftransparency to the polyolefin material prepared therefrom. Moreover,blends of 3,4-DMDBS and EDBS comprising less than, for example, 50 wt. %EDBS have been found to have unsatisfactory dissolution in polyolefinresins such as polypropylene resin. However, EDBS, when used alone or ina blend with 3,4-DMDBS comprising greater than 80 wt. % of EDBS, hasbeen found to confer unsatisfactory organoleptic properties on thenucleated and clarified polyolefin material. In particular, use of EDBSin such amounts leads to a sweet odour associated with the polyolefinmaterial obtained therefrom. This is believed to be associated with thedecomposition of EDBS during processing, leading to formation of theethyl substituted benzaldehyde component, which has a sweet odour.

A further advantage of using the above described blends of 3,4-DMDBS andEDBS is that the polyolefin material clarified and nucleated with theseagents at the weight ratio according to the invention possess desirableorganoleptic properties, having no odour normally associated with theuse of EDBS.

Nevertheless, blends of EDBS and 3,4-DMDBS where the concentration ofEDBS in the blend is as high as 85 wt. % can still confer benefits,provided the resin composition is processed at temperatures of no morethan 200° C. In particular, it has been found to be possible to preparenucleated and clarified polyolefin material from a polyolefin resincomposition comprising bis-3,4-dimethylbenzylidene sorbitol andbis-p-ethylbenzylidene sorbitol in a weight ratio of from 45:55 to 15:85(as in the alternative aspect of the present invention) usingtemperatures of 200° C. or lower without the polyolefin materialsuffering from unsatisfactory organoleptic properties, which wouldotherwise result from the use of EDBS alone.

The concentration of 3,4-DMDBS and EDBS used in the polyolefin resincomposition is not specifically limited and can be suitably determinedover a wide range insofar as the contemplated effects are attainable.Suitably, the total concentration of 3,4-DMDBS and EDBS in thepolyolefin resin composition is from 1000 ppm to 5000 ppm, by weight ofthe polyolef in resin composition. In some embodiments, the totalconcentration of 3,4-DMDBS and EDBS in the polyolefin resin compositionis from 1500 ppm to 4000 ppm, by weight of the polyolef in resincomposition. In some embodiments, the total concentration of 3,4-DMDBSand EDBS in the polyolefin resin composition is from 2250 ppm to 3250ppm, by weight of the polyolef in resin composition, for example 2500ppm or 3000 ppm. In some embodiments, the total concentration of3,4-DMDBS and EDBS in the polyolefin resin composition is from 1500 ppmto 2500 ppm, by weight of the polyolefin resin composition; preferablyfrom 1750 ppm to 2250 ppm, by weight of the polyolefin resincomposition; more preferably from 1900 ppm to 2100 ppm, by weight of thepolyolefin resin composition, for example 2000 ppm.

Where reference is made herein to processing the polyolefin resincomposition in order to form the clarified and nucleated polyolefinmaterial, this may be by any suitable means of which the skilled personis aware. Suitably, any of the conventional moulding methods can beemployed to mould the resin composition of the invention. Illustrativeof such moulding methods are injection moulding, injection stretchmoulding, extrusion moulding, blow moulding, vacuum moulding, rotationalmoulding and film moulding. Thus, for example, the polyolefin resincomposition may first be prepared by blending the crystalline resindirectly with the one or more optical brighteners and nucleating andclarifying agents of the invention in the specific ratio, before theresulting mixture is moulded into the desired product. Alternatively,the one or more optical brighteners and the nucleating and clarifyingagents may be incorporated into the resin before pelletizing themixture, and thereafter moulding the same into the polyolefin material.

The weight ratio of 3,4-DMDBS to EDBS in the resulting polyolefinmaterial formed after processing of the polyolef in resin compositionmay suitably be verified by ¹H NMR analysis.

It has been found that the effects of the present invention may beenhanced if the blend of 3,4-DMDBS and EDBS, as well as the one or moreoptical brighteners, is melt compounded with the polyolef in resin andextruded before the resulting polyolefin resin composition is processedto form the polyolefin material. In particular, it has surprisingly beenfound that a greater reduction in haze values is exhibited by meltcompounding and extruding the resin composition prior to moulding toprepare the polyolefin material in comparison to simply mixing thecomponents of the resin composition and moulding only. These effects areillustrated by the examples provided hereinbelow.

Thus, in preferred embodiments, the methods of the present inventioninclude a step of melt compounding and extruding the components of thepolyolefin resin composition prior to processing to form the polyolef inmaterial. In particularly preferred embodiments, the methods of thepresent invention include a step of melt compounding and extruding thecomponents of the polyolefin resin composition before the resultingpolyolefin resin composition is injection moulded to form the polyolefin material.

Preferably, the polyolefin material which may be prepared in accordancewith the present invention has a haze value, as measured in accordancewith ASTM D1003-61 for a 2 mm thick plaque, of below 45%, morepreferably below 42%, still more preferably below 40%, most preferablybelow 38%, for example 37%, or 36%. Preferably, these levels of haze areobtained by processing the polyolef in resin composition at temperaturesbelow 200° C., for example from 185° C. to 198° C., more preferably at atemperature of from 190° C. to 197° C., most preferably from 190° C. to195° C.

Preferably, the polyolefin material which may be prepared in accordancewith the present invention has a haze value, as measured in accordancewith ASTM D1003-61 for a 1 mm thick plaque, of below 20%, morepreferably below 15%, still more preferably below 13%, most preferablybelow 12%, for example 11%, or 10%. Preferably, these levels of haze areobtained by processing the polyolef in resin composition at temperaturesbelow 200° C., for example from 180° C. to 200° C., preferably from 185°C. to 198° C., even more preferably at a temperature of from 190° C. to197° C., most preferably from 190° C. to 195° C.

Preferably, the polyolefin material which may be prepared in accordancewith the present invention has a haze value, as measured in accordancewith ASTM D1003-61 for a 0.5 mm thick plaque, of below 15%, morepreferably below 10%, still more preferably below 8%, most preferablybelow 6%, for example 5%, or 4%. Preferably, these levels of haze areobtained by processing the polyolefin resin composition at temperaturesbelow 200° C., for example from 180° C. to 200° C., preferably from 185°C. to 198° C., even more preferably at a temperature of from 190° C. to197° C., most preferably from 190° C. to 195° C.

Preferably, the polyolefin material which may be prepared in accordancewith the present invention has a Yellowness Index (YI), as measured inaccordance with ASTM E313 for a 2 mm thick plaque, of less than 7.5,more preferably less than 5, even more preferably less than 2.5, mostpreferably less than 0.5. Preferably, these levels of Yellowness Indexare obtained by processing the polyolefin resin composition attemperatures below 200° C., for example from 180° C. to 200° C.,preferably from 185° C. to 198° C., even more preferably at atemperature of from 190° C. to 197° C., most preferably from 190° C. to195° C.

In still a further aspect, the present invention provides a polyolefinmaterial prepared from a polyolefin resin comprising one or more opticalbrighteners and having a melt flow rate of least 40 g/10 min, asmeasured in accordance with ASTM method D1238-04, which when moulded,preferably injection moulded, at 180° C. has a haze value of less than20%, as measured in accordance with ASTM D1003-61 for a plaque of 1 mmthickness and a and a Yellowness Index of less than 2.5, as measured inaccordance with ASTM E313 for a 2 mm thick plaque. Prior to the methodof the present invention, it is believed not to have been possible toproduce a polyolef in material having such a low haze and low YellownessIndex from a polyolefin resin composition having a relatively high meltflow rate (i.e. at least 40 g/10 min) at a moulding temperature of 180°C.

Preferably, the polyolef in resin has a melt flow rate of less than 500g/10 min, as measured in accordance with ASTM method D1238-04,preferably less than 200 g/10 min, more preferably less than 150 g/10min.

In yet a further aspect, the present invention also provides the use ofa combination of one or more optical brighteners,bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitolin a bis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidenesorbitol weight ratio of 45:55 to 25:75 in the preparation of anucleated and/or clarified polyolefin material, for broadening theprocessing temperature over which a nucleated and/or clarified polyolefin material may be prepared in comparison with the preparation of anucleated and/or clarified polyolefin material usingbis-3,4-dimethylbenzylidene sorbitol or bis-p-ethylbenzylidene sorbitolas the sole clarifying and/or nucleating agent; wherein the haze valueof the nucleated and/or clarified polyolefin material is less than 20%,as measured in accordance with ASTM D1003-61 for a plaque of 1 mmthickness, and the Yellowness Index of the nucleated and/or clarifiedpolyolefin material is less than 2.5, as measured in accordance withASTM E313 for a 2 mm thick plaque.

In yet another aspect, the present invention provides the use of acombination of one or more optical brighteners,bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitolin the preparation of a nucleated and/or clarified polyolefin materialat processing temperatures of 200° C. or below.

In yet another aspect, the present invention provides the use of acombination of one or more optical brighteners,bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitolin the preparation of a nucleated and/or clarified polyolefin materialhaving a haze value of less than 20%, measured in accordance with ASTMD1003-61 for a plaque of 1 mm thickness, and having a Yellowness Indexof less than 2.5, as measured in accordance with ASTM E313 for a 2 mmthick plaque, at processing temperatures of 200° C. or below.

The present invention will now be illustrated by way of the followingexamples and with reference to the following figures:

FIG. 1: Graphical representation for solubility point (° C.)determination from the maximum value for relative brightness variabilityfor different concentrations of 3,4-DMDBS in a molten propylene randomcopolymer resin (MFR 7 g/10 min);

FIG. 2: Graphical representation of the solubility point (° C.) fordifferent concentrations of 3,4-DMDBS, EDBS and blends thereof in amolten propylene random copolymer resin (MFR 7 g/10 min);

FIG. 3: Graphical representation of solubility point (° C.) for variousblends of 3,4-DMDBS and EDBS in molten propylene random copolymer resin(MFR 7 g/10 min), at a combined concentration of 3000 ppm, based on thetotal weight of the resin composition, as well as haze values for apolyolefin material prepared by injection moulding the correspondingresin composition at 180° C. (“IM-180° C”);

FIG. 4: Graphical representation of solubility point (° C.) for variousblends of 3,4-DMDBS and EDBS in molten propylene random copolymer resin(MFR 7 g/10 min), at a combined concentration of 3000 ppm, based on thetotal weight of the resin composition, as well as haze values for apolyolefin material prepared by injection moulding the correspondingresin composition at 190° C. (“IM-190° C”);

FIG. 5: Graphical representation of solubility point (° C.) for variousblends of 3,4-DMDBS and EDBS in molten propylene random copolymer resin(MFR 7 g/10 min), at a combined concentration of 2500 ppm, based on thetotal weight of the resin composition, as well as haze values for apolyolefin material prepared by injection moulding the correspondingresin composition at 180° C. (“IM-180° C”);

FIG. 6: Graphical representation of solubility point (° C.) for variousblends of 3,4-DMDBS and EDBS in molten propylene random copolymer resin(MFR 7 g/10 min), at a combined concentration of 2500 ppm, based on thetotal weight of the resin composition, as well as haze values for apolyolefin material prepared by injection moulding the correspondingresin composition at 190° C. (“IM-190° C”);

FIG. 7: Graphical representation of solubility point (° C.) for variousblends of 3,4-DMDBS and EDBS in molten propylene random copolymer resin(MFR 80 g/10 min), at a combined concentration of 2500 ppm, based on thetotal weight of the resin composition, as well as haze values for apolyolefin material prepared by injection moulding the correspondingresin composition at 180° C. (“IM-180° C”);

FIG. 8: Graphical representation of solubility point (° C.) for variousblends of 3,4-DMDBS and EDBS in molten propylene random copolymer resin(MFR 50 g/10 min), at a combined concentration of 2500 ppm, based on thetotal weight of the resin composition, as well as haze values for apolyolefin material prepared by injection moulding the correspondingresin composition at 180° C. (“IM-180° C”);

FIG. 9: Graphical representation of solubility point (° C.) for variousblends of 3,4-DMDBS and EDBS which also comprise in molten propylenerandom copolymer resin (MFR 50 g/10 min), at a combined concentration of3000 ppm, based on the total weight of the resin composition, as well ashaze values for a polyolefin material prepared by injection moulding thecorresponding resin composition at 180° C. (“IM-180° C”); and

FIG. 10: Graphical representation of melting points for 3,4-DMDBS, EDBSand blends thereof.

EXAMPLES

Solubility Point

The solubility point (° C.) was measured using compounded pelletizedsamples of base resin (described in further detail below). Theparticular compounded pellets were melt compounded at 190° C., therebyavoiding complete dissolution of the clarifier/nucleating agent. Theclarifier/nucleating agent containing pellets were melted above thepolyolef in's softening point (>160° C.) at a rate of 10° C./min up to230° C. As the temperature increased, the clarifier/nucleating agentdispersion eventually dissolved completely into the molten resin and thetemperature was recorded following completion of the phase change.Molten pellets were observed using a microscope (BX41, Olympus) with hotstage (FP90, Mettler) and microscope digital camera system (PixeLINKMicroscopy Camera).

Changes in light transmittance/brightness were recorded by a camerasystem and analysed by means of a computer software program (PixeLINKMicroscopy Software—Capture Standard Edition). From the lighttransmittance/brightness data, the solubility point was determined basedon the temperature at which maximum relative brightness variability wasobserved in a plot of relative brightness variability versustemperature.

FIG. 1 corresponds to the plot observed when determining the solubilitypoint of different concentrations (1000, 2000, 3000 and 4000 ppm) of3,4-DMDBS in molten polypropylene “RACO” MFR 7 g/10 min. Maximum valuesfor relative brightness variability and corresponding temperature(solubility point) are shown to increase as the concentration of3,4-DMDBS in the molten resin composition is increased. FIG. 1illustrates, by virtue of the changing relative brightness variability,that significant dissolution of the clarifier/nucleating agent in theresin composition is observed at temperatures below the measuredsolubility point.

Haze Value

The haze value of the polyolefin material formed was measured accordingto ASTM Standard Test Method D1003-61 “Standard Test Method for Haze andLuminous Transmittance of Transparent Plastics” using a Gardner HazegardPlus.

General Procedure for Preparation of Polyolefin Material

The base resin (random copolymer, hereinafter “RACO”) and all additiveswere weighed and then blended in a Super mixer for 2 minutes at 1500rpm. All samples were then melt compounded on a twin screw extruder at aramped temperature from about 170° C. to 185° C. The melt temperatureupon exit of the extruder die was about 190° C. Pelletized samples weresubsequently used for solubility point measurements. Plaques of thetarget polyolef in material were then made on 25 ton injection moulderusing the pelletized samples. The moulder barrel was set at the specifictemperature indicated below. Plaques were prepared having dimensions of75 mm×75 mm×Z mm, where thickness, Z, is 0.5. mm, 1 mm or 2 mm, using amirror-polished mould. Cooling circulating water in the mould wascontrolled at a temperature of 20° C. Once prepared, the plaques wererested for 24 hours at room temperature before being analysed todetermine their respective Haze values.

The polyolefin base resin used in the present examples was apolypropylene of the following composition:

Polypropylene random copolymer powder 1000 g Irganox ® 1010, PrimaryAntioxidant (from BASF) 500 ppm Irgafos ® 168, Secondary Antioxidant(from BASF) 500 ppm Calcium Stearate, Acid Scavenger 500 ppm Clarifyingcompounds or compositions (as indicated below)

Mixtures of 3,4-DMDBS and EDBS were prepared by admixing the twocomponents in powder form at the desired ratio, before being blendedwith the base resin as described above.

3,4-DMDBS was obtained from New Japan Chemical (Geniset® DXR). EDBS wasprepared in accordance with the following method. A 5 L reaction kettle,equipped with a stirrer and nitrogen inlet, was charged with 400 g ofsorbitol in 2400 g of methanol. 416 g of ethylbenzaldehyde and acatalyst methanol solution (6g of p-toluenesulfonic acid in 100g ofmethanol) were added to the reaction vessel. The solution was stirred at50° C. for 24 hours, during which time a white precipitate formed, whichwas isolated by filtration and washed with methanol to give a whitepowder. The powder was suspended at pH 8 with a small amount of KOH, andthe suspension heated to boiling point, then filtered. The white powderobtained was washed with boiling water and further neutralized to pH 7.The suspension was heated to boiling point before being filtered. Theprecipitated white powder obtained was rinsed with methanol before afurther filtration afforded a white solid. The isolated white powder wasdried in a vacuum oven at 80° C. to give 370 g of EDBS product having apurity above 99% (58 yield).

Example 1

The solubility points of 3,4-DMDBS and EDBS at different concentrationsin molten polypropylene “RACO” MFR 7 g/10 min were determined and theresults are provided below in Table 1.

TABLE 1 3,4- 3,4- Solubility DMDBS EDBS DMDBS:EDBS Point (ppm) (ppm)ratio (° C.) 1000 0 100:0  199 1400 0 100:0  204 1600 0 100:0  207 18000 100:0  210 2000 0 100:0  212 3000 0 100:0  219 4000 0 100:0  225 02000  0:100 190 0 2500  0:100 194 0 3000  0:100 197 0 4000  0:100 203750 1750 30:70 190 1000 1500 40:60 194 1250 1250 50:50 200 900 210030:70 191 1200 1800 40:60 196 1500 1500 50:50 202

The results in Table 1 show that EDBS is highly soluble in moltenpolypropylene, even at high concentrations (e.g. 4000 ppm), having asolubility point significantly lower than that of 3,4-DMDBS atequivalent concentrations. However, EDBS alone has less favourableorganoleptic properties, as described above. Furthermore, blends of3,4-DMDBS and EDBS at a weight ratio in accordance with the inventionhave lower solubility points than 3,4-DMDBS and even EDBS, when usedalone at the same concentration as the total blend concentration and inthe same polyolefin resin.

For example, at a concentration of 3000 ppm, the solubility point of3,4-DMDBS in the polypropylene random copolymer resin was observed to be219° C. and, at a concentration of 3000 ppm, the solubility point ofEDBS in the same polypropylene random copolymer resin was observed to be197° C. In contrast, a blend of 3,4-DMDBS and EDBS in a ratio accordingto the invention (30:70) at a combined concentration of 3000 ppm (900ppm+2100 ppm) in the same polypropylene random copolymer resin wasobserved to be 191° C. Notably, a blend of 3,4-DMDBS and EDBS at aweight ratio not in accordance with the invention (50:50) at a combinedconcentration of 3000 ppm (1500 ppm+1500 ppm) in the same polypropylenerandom copolymer resin was observed to be 202° C., significantly higherthan the solubility point of EDBS at a concentration of 3000 ppm in thesame polypropylene random copolymer resin.

A selection of the above results is also represented graphically in FIG.2, from which the synergistic effects of the blend of 3,4-DMDBS and EDBSat a weight ratio according to the invention can be seen.

Example 2

The solubility points of 3,4-DMDBS, EDBS and blends thereof at differentconcentrations in molten polypropylene “RACO” MFR 7 g/10 min weredetermined followed by determination of haze values for polypropylenematerials prepared therefrom in accordance with the general proceduredescribed above. The results are provided in Table 2 below.

TABLE 2 3,4- Solu- Haze (ASTM- 3,4- DMDBS: bility D1003-61—1 mm) DMDBSEDBS EDBS Point IM- IM- IM- (ppm) (ppm) ratio (° C.) 180° C. 190° C.200° C. 2000 0 100:0  212 28.9 17.2 10.6 0 1500  0:100 — 12.9 12.8 13.20 2000  0:100 190 11.6 11.8 12.4 0 2500  0:100 194 11.9 11.3 12.0 0 3000 0:100 197 11.9 11.1 11.5 250 2250 10:90 194 11.3 11.0 11.3 500 200020:80 194 11.1 10.9 — 750 1750 30:70 190 11.2 11.6 12.0 1000 1500 40:60194 11.9 10.9 12.0 1250 1250 50:50 200 18.8 10.7 11.1 1500 1000 60:40204 22.6 11.2 10.3 1750 750 70:30 207 26.9 19.6 10.8 2000 500 80:20 21227.9 17.7 10.1 2250 250 90:10 212 30.1 20.1 9.5 300 2700 10:90 194 11.210.5 11.0 600 2400 20:80 194 10.3 10.4 10.5 900 2100 30:70 191 10.6 10.411.3 1200 1800 40:60 196 13.0 9.9 10.3 1500 1500 50:50 202 19.7 9.8 10.11800 1200 60:40 206 23.8 12.5 10.1 2000 1000 66:33 208 25.2 13.7 10.52100 900 70:30 213 26.6 18.4 9.9 2400 600 80:20 213 30.5 28.1 9.6 2700300 90:10 219 34.3 29.6 9.5 2000 1000 66:33 208 25.2 13.7 10.5 2000 150057:43 208 22.2 11.6 9.5 2000 2000 50:50 209 24.0 11.7 9.4

The results in Table 2 were used to prepare Haze Value/Solubility Pointplots against 3,4-DMDBS:EDBS ratio for the total concentrations in resin(2500 ppm or 3000 ppm) and for different injection moulding temperatures(180° C. and 190° C.). These plots correspond to FIGS. 3 to 6. Theresults in Table 2, and FIGS. 3 to 6, demonstrate the synergisticeffects in terms of solubility of the nucleating and clarifying agentsand transparency of the polyolef in material prepared, which aresimultaneously observed at 3,4-DMDBS:EDBS ratios according to theinvention. In particular, these synergistic effects are observed at thelower than conventional injection moulding temperatures of 180° C. and190° C. The results in Table 2 also demonstrate that suitable hazevalues are also obtained at higher injection moulding temperatures (200°C.), demonstrating that the invention can also be applied atconventional processing temperatures. Polyolefin materials preparedcomprising 3,4-DMDBS and EDBS in a weight ratio in accordance with thepresent invention had good organoleptic properties. This is in contrastto polyolef in materials prepared with EDBS alone, which had anoticeable sweet odour. Meanwhile, adequate haze and organolepticproperties in nucleated and clarified polyolefin material is also shownto be possible where the weight ratio of bis-3,4-dimethylbenzylidenesorbitol to bis-p-ethylbenzylidene sorbitol used in the polyolefin resincomposition is as high as 15:85 (as in the alternative aspect of thepresent invention), provided processing temperatures do not exceed 200°C.

Example 3

The solubility points of 3,4-DMDBS, EDBS and blends thereof at differentconcentrations in molten polypropylene “RACO” MFR 80 g/10 min weredetermined followed by determination of haze values for polypropylenematerials prepared therefrom in accordance with the general proceduredescribed above. The results are provided in Table 3 below.

TABLE 3 3,4- Haze (ASTM- 3,4- DMDBS: Solubility D1003-61—1 mm) DMDBSEDBS EDBS Point IM- IM- IM- (ppm) (ppm) ratio (° C.) 180° C. 190° C.200° C. 2000 0 100:0  215 47.7 45.9 12.6 2500 0 100:0  219 48.6 45.428.8 3000 0 100:0  223 51.2 47.5 37.8 0 2000  0:100 — 23.1 18.9 19.0 02500  0:100 187 24.3 19.1 18.4 0 3000  0:100 194 28.2 18.6 18.0 600 140030:70 195 18.7 17.9 18.2 800 1200 40:60 200 20.5 18.0 20.5 750 175030:70 196 18.9 16.9 16.9 1000 1500 40:60 202 20.3 14.4 13.5 900 210030:70 200 20.8 13.3 13.6 1200 1800 40:60 205 23.8 13.0 12.7

The results in Table 3 were used to prepare the Haze Value/SolubilityPoint plot against 3,4-DMDBS:EDBS ratio corresponding to FIG. 7 for atotal concentration in resin of 2500 ppm and for an injection mouldingtemperature of 180° C. FIG. 7 and the results in Table 3 furtherdemonstrate the synergistic effects described hereinbefore for ratios of3,4-DMDBS to EDBS according to the invention with a polypropylene resinhaving a high MFR value (80 g/10 min). Polyolefin materials preparedcomprising 3,4-DMDBS and EDBS in a weight ratio in accordance with thepresent invention had good organoleptic properties. This is in contrastto the polyolef in materials prepared with EDBS alone, which had anoticeable sweet odour.

Example 4

The solubility points of 3,4-DMDBS, EDBS and blends thereof at differentconcentrations in molten polypropylene “RACO” MFR 80 g/10 min weredetermined followed by determination of haze values for polypropylenematerials prepared therefrom (0.5 mm plaque thickness) in accordancewith the general procedure described above. The results are provided inTable 4 below.

TABLE 4 3,4- 3,4- Solubility Haze (ASTM- DMDBS EDBS DMDBS:EDBS PointD1003-61—0.5 mm) (ppm) (ppm) ratio (° C.) IM-190° C. IM-200° C. 2500 0100:0  219 20.0 11.1 750 1750 30:70 195 3.7 3.5 1000 1500 40:60 202 3.83.8 0 2500  0:100 187 8.3 4.2

The results in Table 4 further demonstrate the synergistic effectsdescribed hereinbefore for ratios of 3,4-DMDBS to EDBS according to theinvention with a polypropylene resin having a high MFR value (80 g/10min). Polyolefin materials prepared comprising 3,4-DMDBS and EDBS in aweight ratio in accordance with the present invention had goodorganoleptic properties. This is in contrast to the polyolefin materialprepared with EDBS alone, which had a noticeable sweet odour.

Example 5

The solubility points of 3,4-DMDBS, EDBS and blends thereof at differentconcentrations in molten polypropylene “RACO” MFR 80 g/10 min weredetermined followed by determination of haze values for polypropylenematerials prepared therefrom (2.00 mm plaque thickness) in accordancewith the general procedure described above. The results are provided inTable 5 below.

TABLE 5 3,4- 3,4- Solubility Haze (ASTM- DMDBS EDBS DMDBS:EDBS PointD1003-61—2.0 mm) (ppm) (ppm) ratio (° C.) IM-190° C. 2500 0 100:0  21977.4 750 1750 30:70 195 37.6 1000 1500 40:60 202 37.8 0 2500  0:100 18743.9

The results in Table 5 further demonstrate the synergistic effectsdescribed hereinbefore for ratios of 3,4-DMDBS to EDBS according to theinvention with a polypropylene resin having a high MFR value (80 g/10min). Polyolefin materials prepared comprising 3,4-DMDBS and EDBS in aweight ratio in accordance with the present invention had goodorganoleptic properties. This is in contrast to the polyolefin materialprepared with EDBS alone, which had a noticeable sweet odour.

Example 6

The solubility points of 3,4-DMDBS, EDBS and blends thereof at differentconcentrations in molten polypropylene “RACO” MFR 50 g/10 min weredetermined. Polyolefin materials were subsequently prepared by injectionmoulding the resin composition at various temperatures and the hazevalues determined as described in the general procedure above. Theresults provided below in Table 6 below.

TABLE 6 3,4- Haze (ASTM- 3,4- DMDBS: Solubility D1003-61—1 mm) DMDBSEDBS EDBS Point IM- IM- IM- (ppm) (ppm) ratio (° C.) 180° C. 190° C.200° C. 2000 0 100:0  212 41.3 33.6 14.8 2500 0 100:0  214 44.1 37.233.4 3000 0 100:0  223 44.0 41.0 36.1 0 2000  0:100 — 21.3 18.4 20.3 02500  0:100 186 22.4 17.6 19.2 0 3000  0:100 195 22.9 17.7 17.6 600 140030:70 194 15.4 15.5 17.3 800 1200 40:60 198 18.8 15.1 16.0 750 175030:70 195 19.2 12.6 14.8 1000 1500 40:60 201 21.0 12.0 13.0 900 210030:70 197 19.3 9.2 15.0 1200 1800 40:60 201 20.1 14.7 12.0

The results in Table 6 were used to prepare Haze Value/Solubility Pointplots against 3,4-DMDBS:EDBS ratio for a total concentration in resin of2500 ppm and 3000 ppm for an injection moulding temperature of 180° C.,corresponding to FIGS. 8 and 9 respectively. FIGS. 7 and 8, and theresults in Table 6, further demonstrate the synergistic effectsdescribed hereinbefore for ratios of 3,4-DMDBS to EDBS according to theinvention with a polypropylene resin having MFR value of 50 g/10 min.Polyolefin materials prepared comprising 3,4-DMDBS and EDBS in a weightratio in accordance with the present invention had good organolepticproperties. This is in contrast to the polyolefin materials preparedwith EDBS alone, which had a noticeable sweet odour.

Example 7

The solubility points of 3,4-DMDBS, EDBS and blends thereof at differentconcentrations in molten polypropylene “RACO” MFR 48 g/10 min weredetermined. Polyolefin materials were subsequently prepared by injectionmoulding the resin composition at various temperatures and the hazevalues determined as described in the general procedure above. Theresults are provided below in Table 7 below.

TABLE 7 3,4- Haze (ASTM- 3,4- DMDBS: Solubility D1003-61—1 mm) DMDBSEDBS EDBS Point IM- IM- IM- (ppm) (ppm) ratio (° C.) 180° C. 190° C.200° C. 2000 0 100:0  211 43.3 39.9 13.4 2500 0 100:0  213 43 41.5 16.33000 0 100:0  — 46.7 45.2 — 0 2000  0:100 — 19.0 19.1 19.3 0 2500  0:100184 21.1 18.1 19.0 0 3000  0:100 193 25.4 17.6 17.7 600 1400 30:70 19317.2 17.9 17.5 800 1200 40:60 195 17.0 16.6 16.4 750 1750 30:70 195 17.514.8 14.7 1000 1500 40:60 198 22.3 14.3 14.0 900 2100 30:70 199 16.113.8 13.7 1200 1800 40:60 202 22.0 13.1 12.1

The results in Table 7 further demonstrate the synergistic effectsdescribed hereinbefore for ratios of 3,4-DMDBS to EDBS according to theinvention with a polypropylene resin having MFR value of 48 g/10 min.Polyolefin materials prepared comprising 3,4-DMDBS and EDBS in a weightratio in accordance with the present invention had good organolepticproperties. This is in contrast to the polyolefin materials preparedwith EDBS alone, which had a noticeable sweet odour.

Example 8

The solubility points of 3,4-DMDBS, EDBS and blends thereof at aconcentration of 2000 ppm in molten polypropylene “RACO” MFR 40 g/10 minwere determined. Polyolefin materials were subsequently prepared byinjection moulding the resin composition at various temperatures and thehaze values determined as described in the general procedure above. Theresults are provided below in Table 8 below.

TABLE 8 3,4- Haze (ASTM- 3,4- DMDBS: Solubility D1003-61—1 mm) DMDBSEDBS EDBS Point IM- IM- IM- (ppm) (ppm) ratio (° C.) 180° C. 190° C.200° C. 0 2000  0:100 193 25.6 18.4 18.8 2000 0 100:0  207 47.4 36 25.1200 1800 10:90 192 19.4 17.3 17.9 400 1600 20:80 191 17.7 15.4 16.0 5001500 25:75 191 14.9 14.9 15.4 600 1400 30:70 190 15.4 14.7 15.3 800 120040:60 190 17.0 15.0 15.2 1000 1000 50:50 191 21.9 15.3 15.4 1200 80060:40 198 29.1 18.2 14.9 1400 600 70:30 203 38.9 20.6 14.4 1600 40080:20 204 43.2 31 13.2 1800 200 90:10 206 48.4 29.8 17.2

The results in Table 8 further demonstrate the synergistic effectsdescribed hereinbefore for ratios of 3,4-DMDBS to EDBS according to theinvention with a polypropylene resin having MFR value of 40 g/10 min.Polyolefin materials prepared comprising 3,4-DMDBS and EDBS in a weightratio in accordance with the present invention had good organolepticproperties. This is in contrast to the polyolefin materials preparedwith EDBS alone, which had a noticeable sweet odour.

Example 9

The haze values were determined for a series of polyolefin materialsprepared from blends of 3,4-DMDBS and EDBS at a concentration of 2000ppm in molten polypropylene “RACO” MFR 40 g/10 min. One set ofpolyolefin materials was prepared by melt compounding the blend of3,4-DMDBS and EDBS and RACO and extruding at 190° C. before injectionmoulding the resin composition at various temperatures. Another set ofpolyolef in materials was prepared by mixing the blend of 3,4-DMDBS andEDBS and powdered RACO before injection moulding at varioustemperatures. The results are provided below in Table 9a and Table 9bbelow.

TABLE 9a preparation includino extrusion Haze (ASTM- 3,4- 3,4-D1003-61—1 mm) DMDBS EDBS DMDBS:EDBS IM- IM- IM- (ppm) (ppm) ratio 180°C. 190° C. 200° C. 0 2000  0:100 25.6 18.4 18.8 400 1600 20:80 19.7 15.416.0 500 1500 25:75 14.9 14.9 15.4 600 1400 30:70 15.4 14.7 15.3 8001200 40:60 17.0 15.0 15.2 2000 0 100:0  21.9 15.3 15.4

TABLE 9b preparation without extrusion 3,4- Haze (ASTM- 3,4- DMDBS:D1003-61—1 mm) DMDBS EDBS EDBS IM- IM- IM- IM- (ppm) (ppm) ratio 170° C.180° C. 190° C. 200° C. 0 2000  0:100 38.8 26.9 20.2 20.7 400 1600 20:8035.6 22.1 16.4 17.4 500 1500 25:75 32.5 15.8 16.3 16.9 600 1400 30:7023.5 16.0 16.3 16.3 800 1200 40:60 27.4 19.7 16.3 16.4 2000 0 100:0 54.9 54.4 39.0 13.5

A comparison of the haze values of Tables 9a and 9b illustrates theadditional advantage of including a melt compounding and extrusion stepprior to moulding of the resin composition in the preparation of thepolyolefin material. In particular, a reduction in haze values isexhibited by melt compounding and extruding the resin composition priorto moulding to prepare the polyolefin material in comparison to justmixing the components of the resin composition and moulding only. Thus,in order to enhance the effects of the present invention, the polyolefin material may be prepared by melt compounding and extruding the resincomposition prior to injection moulding to form the polyolef inmaterial.

Example 10

The melting point of various blends of 3,4-DMDBS and EDBS weredetermined to assess the effect of the relative proportions of thecomponents on the melting point of the blend. Results are provided inTable 10 below together with the solubility points for the majority ofblends in molten polypropylene “RACO” MFR 40 g/10 min at a concentrationof 2000 ppm. Then trend of melting points for the various blends is alsorepresented graphically in FIG. 10.

TABLE 10 3,4-DMDBS EDBS 3,4- m.p. Solubility (ppm) (ppm) DMDBS:EDBSratio (° C.) Point (° C.) 0 2000  0:100 244.9 193 500 1500 25:75 244.0 —600 1400 30:70 241.8 190 800 1200 40:60 241.9 190 1000 1000 50:50 243.7191 1100 900 55:45 249.1 — 1200 800 60:40 251.2 198 1500 500 25:75 257.5— 2000 0 100:0  275.3 207

The results in Table 10 (as well as FIG. 10) illustrate that the meltingpoint of the blend does not merely reflect the respective melting pointsof the two components of the blend and their relative proportions ineach of the blends. Surprisingly, the results indicate that the blendsform a eutectic system having a eutectic point, where the melting pointof the blend is lowest and lower than the respective melting points ofthe individual components alone, for a 3,4-DMDBS to EDBS ratio ofapproximately 30:70. It will also be appreciated that this eutecticblend of 3,4-DMDBS and EDBS also coincides with the blend of 3,4-DMDBSand EDBS exhibiting one of the lowest solubility points in the moltenresin.

The surprising eutectic system exhibited by the blend of 3,4-DMDBS andEDBS is considered to further illustrate the effects of the invention.Without being bound by any particular theory, it is believed that thecorrelation observed between the melting point of the blends and thesolubility point of the blend in molten resin indicates that theeutectic properties of the blend contribute to the ability of the resincomposition to be processed at lower than conventional temperatures toform a clarified and/or nucleated polyolef in material having excellenthaze properties.

Example 11

The solubility points of 3,4-DMDBS, EDBS and blends thereof at aconcentration of 1000 ppm and 5000 ppm in molten polypropylene “RACO”MFR 70 g/10 min were determined. Polyolefin materials were subsequentlyprepared by injection moulding the resin composition at varioustemperatures and the haze values determined as described in the generalprocedure above. The results are provided below in Table 11 below.

TABLE 11 3,4- Solu- Haze (ASTM- 3,4- DMDBS: bility D1003-61—1 mm) DMDBSEDBS EDBS Point IM- IM- IM- (ppm) (ppm) ratio (° C.) 180° C. 190° C.200° C. 1000 0  0:100 198 38.7 25.3 25.8 5000 0  0:100 234 48.4 46.942.5 0 1000 100:0  192 25.8 26.6 28.2 0 5000 100:0  216 23.8 16 13.7 300700 30:70 191 30.7 31.3 31.7 1500 3500 30:70 208 19.5 16.6 12.2 600 40060:40 192 31.8 30.7 32.2 3000 2000 60:40 223 24.7 24.4 18.9

The results in Table 11 further demonstrate the synergistic effectsdescribed hereinbefore for ratios of 3,4-DMDBS to EDBS according to theinvention with a polypropylene resin having MFR value of 70 g/10 min.Polyolefin materials prepared comprising 3,4-DMDBS and EDBS in a weightratio in accordance with the present invention had good organolepticproperties. This is in contrast to the polyolefin materials preparedwith EDBS alone, which had a noticeable sweet odour. The results ofTable 11 also demonstrate that synergistic effects are observed forrelatively low total 3,4-DMDBS and EDBS concentrations (1000 ppm) aswell as relatively high concentrations (5000 ppm).

Example 12

The solubility points of 3,4-DMDBS, EDBS and blends thereof at aconcentration of 1000 ppm and 5000 ppm in molten polypropylene “RACO”MFR 25 g/10 min were determined. Polyolefin materials were subsequentlyprepared by injection moulding the resin composition at varioustemperatures and the haze values determined as described in the generalprocedure above. The results are provided below in Table 12 below.

TABLE 12 3,4- Solu- Haze (ASTM- 3,4- DMDBS: bility D1003-61—1 mm) DMDBSEDBS EDBS Point IM- IM- IM- (ppm) (ppm) ratio (° C.) 180° C. 190° C.200° C. 1000 0  0:100 201 28.7 20.1 20.5 5000 0  0:100 233 47.2 45.742.6 0 1000 100:0  190 17.1 18.3 19.5 0 5000 100:0  219 24.2 15.9 11.9300 700 30:70 196 22 23.5 24.2 1500 3500 30:70 209 19.1 14 9.2 600 40060:40 197 23.2 25.1 26.6 3000 2000 60:40 221 26.9 26.1 18.6

The results in Table 12 further demonstrate the synergistic effectsdescribed hereinbefore for ratios of 3,4-DMDBS to EDBS according to theinvention with a polypropylene resin having MFR value of 25 g/10 min.Polyolefin materials prepared comprising 3,4-DMDBS and EDBS in a weightratio in accordance with the present invention had good organolepticproperties. This is in contrast to the polyolefin materials preparedwith EDBS alone, which had a noticeable sweet odour. The results ofTable 12 also demonstrate that synergistic effects are observed forrelatively low total 3,4-DMDBS and EDBS concentrations (1000 ppm) aswell as relatively high concentrations (5000 ppm).

Example 13

The solubility points of 3,4-DMDBS, EDBS and blends thereof at aconcentration of 1000 ppm and 5000 ppm in molten polypropylene “RACO”MFR 7 g/10 min were determined. Polyolefin materials were subsequentlyprepared by injection moulding the resin composition at varioustemperatures and the haze values determined as described in the generalprocedure above. The results are provided below in Table 13 below.

TABLE 13 3,4- Solu- Haze (ASTM- 3,4- DMDBS: bility D1003-61—1 mm) DMDBSEDBS EDBS Point IM- IM- IM- (ppm) (ppm) ratio (° C.) 180° C. 190° C.200° C. 1000 0  0:100 204 14.5 18.2 17.6 5000 0  0:100 229 41.5 41.4 310 1000 100:0  185 16.5 15.8 15.6 0 5000 100:0  207 13.9 9.3 9.3 300 70030:70 189 18.3 18.1 17.4 1500 3500 30:70 207 16.7 8.5 8.6 600 400 60:40199 18.8 18.9 18.6 3000 2000 60:40 219 28.6 27.5 9.3

The results in Table 13 further demonstrate the synergistic effectsdescribed hereinbefore for ratios of 3,4-DMDBS to EDBS according to theinvention with a polypropylene resin having MFR value of 7 g/10 min.Polyolefin materials prepared comprising 3,4-DMDBS and EDBS in a weightratio in accordance with the present invention had good organolepticproperties. This is in contrast to the polyolefin materials preparedwith EDBS alone, which had a noticeable sweet odour. The results ofTable 13 also demonstrate that synergistic effects are observed forrelatively low total 3,4-DMDBS and EDBS concentrations (1000 ppm) aswell as relatively high concentrations (5000 ppm).

Example 14

The solubility points of blends of 3,4-DMDBS and EDBS (30:70), at aconcentration of 2500 ppm in molten polypropylene “RACO” MFR 70 g/10min, with varying amounts of optical brightener (OB) additive weredetermined. Polyolefin materials were subsequently prepared by injectionmoulding the resin composition at various temperatures and the hazevalues determined as described in the general procedure above. Theoptical brightener (OB) which was used was Ciba® Tinopal® OB(2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene; CAS# 7128-64-5) whichwas sourced from Ciba Specialty Chemicals.

Yellowness Index (YI) for each of the polyolefin materials prepared byinjection moulding at 190° C. was also determined in accordance withASTM E313 for a 2 mm thick plaque. In addition, a 5-member panel judgedthe appearance (based on colour/yellowness and clarity) of this same setof polyolefin materials in a blind test and ranked the differentpolyolef in materials accordingly (1 being the polyolefin material withthe best appearance, 6 being the polyolefin material with the leastappealing appearance). The results are provided in Table 14 below.

TABLE 14 Solu- Haze (ASTM- YI OB bility D1003-61—1 mm) (2 mm) Appearance(wt. Point IM- IM- IM- IM- Test %¹) (° C.) 180° C. 190° C. 200° C. 190°C. 1 2 3 4 5 Av. — 198 16.3 13 12.9 11.6 6 6 6 6 1 5 0.10 195 18.3 12.713.7 8.1 5 5 5 5 6 5.2 0.50 197 18.4 13.2 14 1.5 4 1 4 4 4 3.4 1.00 19816.1 13.3 13.7 −1.9 3 1 3 1 5 2.6 1.50 197 13.5 13.3 14.1 −3.5 1 1 1 1 31.4 2.00 197 14.2 13.3 14 −4.6 2 4 2 1 2 2.2 ¹weight % of opticalbrightener relative to total concentration of nucleator/clarifier²Negative values of YI denote departure toward blue.

The results in Table 14 further demonstrate the synergistic effectsdescribed hereinbefore for ratios of 3,4-DMDBS to EDBS according to theinvention with a polypropylene resin having MFR value of 70 g/10 min.Furthermore, the results in Table 14 demonstrate that these synergisticeffects are not diminished by the presence of optical brightener. Thepresence of optical brightener has a significant impact on reduction ofyellowness, as shown by the substantial reduction in Yellow Index (YI)value. The results of the “blind” appearance test for the polyolefinmaterials prepared having different amounts of optical brightenerdemonstrate that the presence of optical brightener generally improvesthe ranking of the polyolefin material compared to the polyolef inmaterial comprising no optical brightener. Moreover, increasing theamount of optical brightener generally increases the ranking of thepolyolefin material in the appearance test across the concentrationstested.

Example 15

The solubility points of blends of 3,4-DMDBS and EDBS (30:70), at aconcentration of 3000 ppm in molten polypropylene “RACO” MFR 70 g/10min, with varying amounts of optical brightener (OB) additive weredetermined. Polyolefin materials were subsequently prepared by injectionmoulding the resin composition at various temperatures and the hazevalues determined as described in the general procedure above. Theoptical brightener (OB) which was used was Ciba® Tinopal® OB(2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene; CAS# 7128-64-5) whichwas sourced from Ciba Specialty Chemicals.

Yellowness Index (YI) for each of the polyolefin materials prepared byinjection moulding at 190° C. was also determined in accordance withASTM E313 for a 2 mm thick plaque. In addition, a 5-member panel judgedthe appearance (based on colour/yellowness and clarity) of this same setof polyolefin materials in a blind test and ranked the differentpolyolef in materials accordingly (1 being the polyolefin material withthe best appearance, 6 being the polyolefin material with the leastappealing appearance). The results are provided in Table 15 below.

TABLE 15 Solu- Haze (ASTM- YI OB bility D1003-61—1 mm) (2 mm) Appearance(wt. Point IM- IM- IM- IM- Test %¹) (° C.) 180° C. 190° C. 200° C. 190°C. 1 2 3 4 5 Av. — 199 17.1 13.4 12.2 11.7 6 — 6 6 6 6 0.10 201 17.312.1 12.6 6.1 5 — 5 5 5 5 0.50 199 17.7 12.5 12.5 0.4 4 — 4 2 4 3.5 1.00200 17.3 12.9 12.4 −2.4 2 — 2 4 1 2.25 1.50 201 17.8 12.2 12.7 −3.7 3 —3 3 2 2.75 2.00 199 17.6 12 13.2 −4.9 1 — 1 1 3 1.5 ¹weight % of opticalbrightener relative to total concentration of nucleator/clarifier²Negative values of YI denote departure toward blue.

The results in Table 15 further demonstrate the synergistic effectsdescribed hereinbefore for ratios of 3,4-DMDBS to EDBS according to theinvention with a polypropylene resin having MFR value of 70 g/10 min.Furthermore, the results in Table 15 demonstrate that these synergisticeffects are not diminished by the presence of optical brightener. Thepresence of optical brightener has a significant impact on reduction ofyellowness, as shown by the substantial reduction in Yellow Index (YI)value. The results of the “blind” appearance test for the polyolefinmaterials prepared having different amounts of optical brightenerdemonstrate that the presence of optical brightener generally improvesthe ranking of the polyolefin material compared to the polyolef inmaterial comprising no optical brightener. Moreover, increasing theamount of optical brightener generally increases the ranking of thepolyolefin material in the appearance test across the concentrationstested.

1-51. (canceled)
 52. A method for forming a polyolefin material, said method comprising: (i) preparing a polyolefin resin composition comprising polyolefin resin, one or more optical brighteners and bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitol, wherein the weight ratio of bis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitol in the polyolefin resin composition is 45:55 to 25:75; and (ii) processing said polyolefin resin composition to form said polyolefin material.
 53. The method according to claim 52, wherein processing of the polyolefin resin composition to form said polyolefin material is conducted at a temperature of from 180° C. to 245° C.
 54. A method for forming a polyolefin material, said method comprising: (i) preparing a polyolefin resin composition comprising polyolefin resin, one or more optical brighteners, bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitol, wherein the weight ratio of bis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitol in the polyolefin resin composition is 45:55 to 15:85; and (ii) processing said polyolefin resin composition to form said polyolefin material, wherein processing of the polyolefin resin composition to form said polyolefin material is conducted at a temperature of no more than 200° C.
 55. The method according to claim 52, wherein processing of the polyolefin resin composition to form said polyolefin material is conducted at a temperature of from 180° C. to 200° C.
 56. The method according to claim 52, wherein processing of the polyolefin resin composition comprises injection and/or extrusion molding the polyolefin resin composition.
 57. The method according to claim 52, wherein the weight ratio of bis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitol in the polyolefin resin composition is 40:60 to 25:75.
 58. The method according to claim 52, wherein the weight ratio of bis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitol in the polyolefin resin composition is 32:68 to 28:72.
 59. The method according to claim 52, wherein the combined amount of bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitol in the polyolefin resin composition is from 1000 ppm to 5000 ppm, by weight of the polyolefin resin composition.
 60. The method according to claim 52, wherein the one or more optical brighteners are selected from bis-benzoxazoles, phenylcoumarins, methylcoumarins, bis-(styryl)biphenyls, and combinations thereof.
 61. The method according to claim 60, wherein the one or more optical brighteners are selected from 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene, 4,4′-bis-benzoxazolylstilbene, 3-phenyl-7-(4-methyl-6-butyloxybenzoxazole)coumarin and 4-methyl-7-diethylamincoumarin.
 62. The method according to claim 52, wherein the total amount of the one or more optical brighteners in the polyolefin resin composition is from 1 to 100 ppm, by weight of the polyolefin resin composition.
 63. The method according to claim 52, wherein the polyolefin resin has a melt flow rate of 5 g/10 min or above, as measured according to ASTM method D1238-04.
 64. The method according to claim 52, wherein the polyolefin material has a haze value, as measured in accordance with ASTM D1003-61 for a 1 mm thick plaque, of below 20%.
 65. A nucleating and clarifying additive composition comprising or consisting essentially of one or more optical brighteners, bis-3,4-dimethylbenzylidene sorbitol and bis-pethylbenzylidene sorbitol, wherein the weight ratio of bis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitol in the additive composition is 45:55 to 25:75.
 66. The nucleating and clarifying additive composition according to claim 65, wherein the one or more optical brighteners are selected from bis-benzoxazoles, phenylcoumarins, methylcoumarins, bis-(styryl)biphenyls, and combinations thereof.
 67. The nucleating and clarifying additive composition according to claim 66, wherein the one or more optical brighteners are selected from 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene, 4,4′-bis-benzoxazolylstilbene, 3-phenyl-7-(4-methyl-6-butyloxybenzoxazole) coumarin and 4-methyl-7-diethylamincoumarin.
 68. A polyolefin resin composition comprising: polyolefin resin, one or more optical brighteners and bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitol, wherein the weight ratio of bis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitol in the polyolefin resin composition is 45:55 to 25:75.
 69. A polyolefin material comprising: (a) polyolefin; (b) bis-3,4-dimethylbenzylidene sorbitol; (c) bis-p-ethylbenzylidene sorbitol; and (d) one or more optical brighteners; wherein the weight ratio of bis-3,4-dimethylbenzylidene sorbitol to bis-pethylbenzylidene sorbitol in the polyolefin material is from 45:55 to 25:75.
 70. A polyolefin material according to claim 69, wherein i) the polyolefin material has a haze value, as measured in accordance with ASTM D1003-61 for a 1 mm thick plaque, of below 20%, and/or ii) wherein the polyolefin material has a Yellowness index, as measured in accordance with ASTM E313 for a 2 mm thick plaque, of less than 7.5.
 71. A polyolefin material prepared: i) by preparing a polyolefin resin composition comprising polyolefin resin, one or more optical brighteners, bis-3,4-dimethylbenzylidene sorbitol and bis-p-ethylbenzylidene sorbitol, wherein the weight ratio of bis-3,4-dimethylbenzylidene sorbitol to bis-p-ethylbenzylidene sorbitol in the polyolefin resin composition is 45:55 to 15:85; and processing said polyolefin resin composition to form said polyolefin material, wherein processing of the polyolefin resin composition to form said polyolefin material is conducted at a temperature of no more than 200° C.; or ii) from a polyolefin resin comprising one or more optical brighteners having a melt flow rate of least 40 g/10 min, as measured in accordance with ASTM method D1238-04, which when molded at 180° C. has a haze value of less than 20%, as measured in accordance with ASTM D1003-61 for a plaque of 1 mm thickness, and a Yellowness Index of less than 2.5, as measured in accordance with ASTM E313 for a 2 mm thick plaque. 